Linux File system

1. Linux File system Lab6 CPCS361 I.Mona Alshehri

2. Working with Files and Directories • Creating files • Create a file with the cat commandtype the command • cat > name_of_file • Now type in your text. Press the <return> key to start a new line. When you have finished typing in your text, enter ctrl-d (press and hold down the ctrl key and type a "d"). This stops the cat command and returns you to the system prompt. • Text editors while using Linux you will often want to create a text file and then change its content in some way. A text editor is a program that has been designed especially for this purpose. The easiest of all editors is the kwrite editor. Type the command • kwrite name_of_file • The editor will open where you can write your text or program and at bottom of editor window you will see the commands to save, quit or do other changes to text. Just follow those commands.

3. Removing files • To remove a file use the command:   rm filename(s) • You cannot remove a file in another user's account unless they have set access permissions for the file which allow you to. Use the -i (interactive) option which makes the command prompt you for confirmation that you want to remove each file. • To remove a single file:  rm help.txt       This removes the file help.txt from the current directory. • To remove several files: rm file1 file2 file3    This removes files file1, file2, file3 from current directory. • To remove files interactively: rm -i file     This will prompt you to confirm that you want to remove file from the current directory. • Answering y will delete the file. The file is not deleted if any other response is given.

4. Determining file type • The file command examines the content of a file and reports what type of file it is. To use the command enter: file filename • Use this command to check the identity of a file, or to find out if executable files contain shell scripts, or are binaries. Shell scripts are text files and can be displayed and edited.

5. Displaying files • The cat command is useful for displaying short files of a few lines. To display longer files use more that displays files page by page of 25 or so lines. • To display the contents of a file use the commands: cat filename more filename: Progressively dump a file to the screen: ENTER = one line down SPACEBAR = page down q=quit • To display the first n number of lines of a text file use the command:    head –n filename • To display the last n number of lines of a text file use the command:    tail -n filename • Note: Both the head and tail commands displays only first and last 10 lines respectively if the option of -n is not specified or used in command.

6.  Copying files • Copying files in the same directory To create an exact copy of a file use the cp (copy) command. cp old_file new_file • The old_file is the name of the file to be copied; the new_file is the name of the file in which the copy is to be placed. • Copying more than one file You can use special "wildcard" characters whenever you want to copy several files that have similar filenames. Instead of entering the cp command followed by several filenames you can use a single filename that contains one or more wildcards. cp file1 file2 file3 sub_directory or cp file* sub_directory • Copies three files to a sub directory of the current directory. • Copying files to another directory To copy a file to another directory from your current directory give name of the source file followed by the pathname to the destination file. cp source path_to_destination

7.  Copying files • For the destination file to have the same name as the source file use: cp source path_to_destination_directory • To copy a file from your current working directory to a subdirectory: cp fig2 part2/figure2 • This copies the file fig2 from your current working directory to the file figure2 in the subdirectory part2. • To copy a file to the parent directory: cp mail.txt .. • This copies the file mail.txt to the directory immediately above the current working directory with the same name mail.txt. The .. (dot dot) is shorthand for the parent directory.

8.  Copying files • Copying files from another directory To copy a file from another directory to your current directory give the pathname to the source file followed by the name of the destination file. cp path_to_source_file destination • For the destination file to have the same name as the source file use: cp path_to_source_file . • The . (dot) is shorthand for the current working directory. • To copy a file from a subdirectory to the current working directory: cp notes/note3 sect3.txt • This copies the file note3 from the subdirectory notes to the file sect3.txt in the current working directory. A relative pathname notes/note3 is used to define the source file. • To copy a file from another directory to the current working directory, preserving the file name: cp /usr/lib/more.help . • This creates a copy of the file more.help in the current working directory. A full pathname /usr/lib/more.help is used to define the source file.

9. Moving files and directories • To move files and directories from one place to another use the mv (move) command: mv filename1 filename2 directory1 directory2 filename directory • Note: You can also change the name of a file or directory by moving it. • To rename a file: mv junk precious • This renames the file junk as the file precious.

10. Finding a file • To locate a file in the file system , use the find command. find pathname -name filename • The pathname defines the directory to start from. Each subdirectory of this directory will be searched. The -print option must be used to display results. You can define the filename using wildcards. If these are used, the filename must be placed in 'quotes'. • To find a single file below the current directory: find . –name program.c • This displays the pathname to the file program.c starting from the current directory. If the file is not found nothing is displayed. • To find several files below the current directory: • find . -name '*.c' • This displays the pathname to any file with the extension .c which exists below the current directory.

11. Searching the contents of a file • To search a text file for a string of characters or a regular expression use the command: grep pattern filename(s) • Using this command you can check to see if a text file holds specific information. grep is often used to search the output from a command. Any regular expression containing one or more special characters must be quoted to remove their meaning. • To search a file for a simple text string:   grep copying help • This searches the file help for the string copying and displays each line on your terminal. • To search a file using regular expression: grep -n '[dD]on\'t' tasks • This uses a regular expression to find and display each line in the file tasks that contains the pattern don't or Don't. The line number for each line is also displayed. • The expression is quoted to prevent the shell expanding the metacharacters [, ] and '. Double quotes are used to quote the single quote in dDon't.

12. Linking files and directories • To link files and directories use the command: ln source linkname • Making a link to a file or directory does not create another copy of it; it simply makes a connection between the source and the linkname. • To make several links to a file in different directories: ln part1.txt ../helpdata/sect1 /public/helpdoc/part1   This links part1.txt to ../helpdata/sect1 and /public/helpdoc/part1. • Using symbolic links Your files (and directories) may be located on several different file systems. To link files that are in different file systems you need to make a symbolic link. • To make a symbolic link use the command: ln -s source linkname

13. Linking files and directories • To link one or more directories to another directory use the command: • ln -s directory_name(s) directory_name • The use of the -s option indicates that this is to be a symbolic link. Only the super-user is allowed make hard links between directories. As a user you are restricted to creating symbolic links between directories using the -s option. • For example, to link the /usr/local/lib/example directory to /example, use the following command: • ln -s /usr/local/lib/example /example • After creating the symbolic link above, /example will point to /usr/local/lib/example, and when user changes directory (CD) to /example, OS shell will automatically change it to /usr/local/lib/example directory.